Abstract: Technologies are shown for controlling a transaction on a blockchain. A first block is created on a blockchain for a transaction involving a seller entity associated with a first key, a buyer entity associated with a second key, and an intermediary entity associated with a third key. Funds for the transaction are associated with the first block. A second block storing refund code is created and linked to the first block. The refund code is executable to refund the funds when a seller digital signature using the first key and/or an intermediary digital signature using the third key are received. A third block storing payment code is created and linked to the first block. The payment code is executable to transfer the funds when a buyer digital signature using the second key and/or an intermediary digital signature using the third key are received.

Abstract: Technologies are shown for controlling a transaction on a digitally stored blockchain by creating a contract data block for a transaction involving entities and by event code executed after receipt of digital signatures from the entities. A refund transaction may be digitally signed by entities and linked to the contract block within the blockchain. A payment transaction block may also be digitally signed by entities and linked to the contract block. Code authorized to execute by the blocks executes based on receipt of digital signature events.

Abstract: Technologies are shown for controlling a transaction on a digitally stored blockchain by creating a contract data block for a transaction involving entities and by event code executed after receipt of digital signatures from the entities. A refund transaction may be digitally signed by entities and linked to the contract block within the blockchain. A payment transaction block may also be digitally signed by entities and linked to the contract block. Code authorized to execute by the blocks executes based on receipt of digital signature events.

Abstract: Example methods and systems are directed to generating recommendations based on one or more user inventories, which may be stored in a database. The inventory may include items (e.g., physical goods, electronic goods, and financial assets) owned by a user. A machine may use the database to provide suggestions to the user to buy or sell items. The machine may also use the database to provide suggestions to the user to join a community. The database may be used in conjunction with an electronic commerce site. The machine may be aware of which items in the site are being viewed by the user. The recommendation made by the machine may take into account the item being viewed. The user may be able to view the current market value for each item individually, the total value for a selection of items, or the total value for all items.

Abstract: A system, method, and computer readable medium are provided to manage an inventory across multiple sales channels. A first set of items from an inventory is listed on a first sales channel according to a business rule. A second set of items from the inventory is listed on a second sales channel according to the business rule. Order events from the first sales channel and the second sales channel are tracked. The order events may indicate a transaction involving an item from the inventory. The business rule may be used to rebalance items still offered for sale on the first sales channel and the second sales channel.